This application relates to fibers and fiber devices.
Optical fiber can be used to generate variable optical delays by controlling the length of a fiber loop. For example, multiple turns of optical fiber can be wound around a cylindrical piezo-electric (PZT) actuator to form a fiber optical delay device where an electrical voltage is applied to the cylindrical PZT actuator to cause the diameter of the cylindrical PZT actuator to change. This change leads to a change in the circumference of the cylindrical PZT actuator and thus changes the level of stretching on the fiber loop. This design can be used to achieve fast delay variations and was described by Tearney et al. in an article entitled “Rapid acquisition of a in vivo biological images by use of optical coherence tomography,” Optics Letters, Vol. 21, pp. 1408-1410 (1996). The response speed of such a PZT-based fiber delay device can be fast, e.g., on the order of KHz or tens of kHz.
Other variable optical devices have also been proposed for achieving fast delay variations. Examples include a delay device based on a rotating cube described by Su in “Achieving variation of optical path length by a few millimeters at millisecond rates for imaging turbid media and optical interferometry: A new technique,” Optics Letters, Vol. 22, pp. 665-667 (1997), a delay device based on a rotating mirror pair by Yasa et al. in “A rapid scanning autocorrelation scheme for continuous monitoring of picosecond pulses,” Optical communications, Vol. 36, pp. 406-408 (1981), a grating based Fourier domain resonant delay line disclosed by Tearney et al. in “High speed phase- and group-delay scanning with a grating-based phase control delay line,” Optics Letters, Vol. 22, pp. 1811-1813 (1997), and an accousto-optic modulator based delay line by Yang et al. in “Rapid ultrafine-tunable optical delay line at the 1.55 um wavelength,” Optics Letters, Vol. 23, pp. 1843-1845 (1998).
Fiber-based optical delay devices can be easily interfaced or integrated with fiber components and devices to provide various advantages. For example, fiber based devices can be designed to avoid alignment of optical components in free space or to achieve compact device packaging.